Multi-phase transformer



Dec. 4, 1962 J. C. NYGARD MULTI-PHASE TRANSFORMER Filed Jan. 5, 1960 United States Patent 3,067,374 MULTI-PHASE TRANSFORMER John C. Nygard, Lexington, 'Mass, assignor to High Voltage Engineering Corporation, Burlington, Mass., a

corporation of Massachusetts Filed Jan. 5, 1960, Ser, No. 564 4 Claims. (Cl. 321-8) This invention relates to high voltage electromagnetic apparatus of the insulating-core type disclosed and claimed in a co-pending application, Serial Number 647,915, assigned to the assignee of the present application, and now abandoned. In particular, this invention relates to a multi-phase transformer design especially suited to high voltage high power applications.

The invention may best be understood from the following detailed description thereof having reference to the accompanying drawing in which:

FIG. 1 is a view generally in horizontal central section showing the circuitry and construction of a-transformer constructed in accordance with the invention and adapted to three-phase operation;

FIG. 2 is a side view, partly broken away, of the apparatus of FIG. 1;

FIG. 3 is a circuit diagram of the secondary windings of the apparatus of FIGS. 1 and 2; and

FIG. 4 is a perspective view showing a modification of the apparatus of FIGS. 1 and 2.

Referring to the drawings, and first to FIGS. 1 and 2 thereof, the high voltage terminal of the high voltage transformer therein shown comprises a spherical electrode 1 which is supported in a central position upon a plurality of columns 2. These columns 2 extend radially outward from the high voltage terminal sphere 1, and the other ends thereof are supported upon grounded parts of the apparatus. In FIGS. 1 and 2 the grounded ends of the columns 2 are shown as being supported upon an annulus 3 of magnetic material which also serves as part of the magnetic circuit.

The magnetic circuit is thus seen to comprise the central high voltage terminal 1, the radial columns 2, and the outer rim 3. The columns 2 must be able to support the potential difference between the high voltage terminal sphere 1 and the outer grounded rim 3, and accordingly should be constructed in accordance with the teachings of US. patent application No. 647,915. For example, each column 2 may comprise ferromagnetic material having at least two gaps 4 each crossing a substantial portion of the lines of magnetic flux and together insulating a potential difference in excess of 10 kilovolts, the ratio of the length of each gap 4 to the area thereof being small so as to reduce the reluctance of the gap. Secondary windings 5 are wound about the columns 2 and primary windings 6 are wound about those portions of the outer rim 3 which lie between extremities of adjacent columns 2. When relatively low voltage electric power is applied to the primary windings 6, relatively high voltage is produced at the high voltage terminal sphere 1 in accordance with well known transformer principles. The input power which is applied to each primary winding 6 is out of phase with the input power applied to the other primary windings 6 so that, in accordance with well known principles of multi-phase transformer design, a similar multi-phase output is obtained at the high voltage terminal 1. Thus, in the device shown in FIGS. 1 and 2 there would be a three-phase input with a displacement of 120 between the phase of any two primaries 6 and a similar three phase output at the high voltage terminal sphere l, the currents in any two secondary windings 5 being mutually out of phase by 120. The advantage of multi-phase operation in the generation of high voltage is, of course, the reducice tion of ripple in the generation of DC. voltage. This advantageous result follows whether the high voltage out put is rectified in the conventional manner or whether a plurality of increments in the secondary windings are separately rectified in accordance with teachings of said patent application Serial No. 647,915. For illustrative purposes only, the secondary windings 5 of FIGS. 1 and 2 may be constructed, in a manner shown in detail in said patent application Serial No. 647,915, S0 as to form the circuit shown in the diagram of FIG. 3.

It is to be understood that the invention is not limited to a three-phase device but comprehends any number of phases such as six, twelve or even more. Additional phases may be provided merely by increasing the number of spokes, as it were, to the wheel; that is to say, by increasing the number of columns extending radially outward from the central high voltage terminal to the grounded rim, as shown in FIG. 4. The invention comprehends the geometrical configure tion wherein a rounded high voltage terminal is centrally located, and the secondary coils by means of which electric charge is delivered to the high voltage terminal are radially disposed about the high voltage terminal, the magnetic circuit being closed by grounded members in an appropriate manner. Such a geometry provides an excellent high voltage electrostatic configuration since the electrical equipotentials are spheres. Even more favorable is the magnetic configuration resulting from the geometrical configuration of the invention, since such geometrical configuration provides the lowest possible leakage reactance and leakage magnetic flux. The leakage reactance depends upon the relative length of the windings; that is to say, the more nearly the length of the primary winding approaches that of the secondary winding, the lower the leakage reactance losses. In other transformer configurations not constructed in accordance with the invention, increasing the length of the primary winding serves markedly to increase the size of the transformer owing to the electrical insulation requirements and other factors. However, in the geometrical configuration of the invention the primary winding may be made very long without the necessity for enlarging the dimensions of the apparatus.

As a consequence, the entire apparatus may be placed in a tank 7 filled with insulating gas under pressure for the attainment of higher voltages, and this tank may be a spherical low cost type whereby, for example, 5 million volts can be housed in a 25 foot diameter sphere rated at 50 to milliamperes or more.

Of course, as the number of phases is increased by increasing the number of columns, if the columns are all added in the same plane, as it were, the length available for the primary windings will decrease. However, the geometry of the configuration of the invention does not require that the additional columns be placed in the same plane, so that additional phases may be provided without reducing the available length of the primary winding, as, for example, by the spherical construction shown in FIG. 4.

Having thus described the principles of .the invention together with illustrative embodiments thereof, it is to be understood that although specific terms are employed, they are used in a generic and descriptive sense and not for purposes of limitation, the scope of the invention being set forth in the following claims.

I claim:

1. A multi-phase high voltage transformer comprising a rounded high voltage terminal, a plurality of magnetic columns having electrically insulating properties along the lines of magnetic flux extending radially outward from said high voltage terminal, grounded magnetic circuit elea ments connecting the peripheral extremities of said insulating cores, a plurality of coils linking said columns and electrically connected between said high voltage terminal and said groundedmagnetic elements, and means other than said coils for introducing fluctuations in the magnetic flux in said columns, whereby multi-phase. high voltage is produced at said high voltage terminal.

2. A multi-phase high voltage transformer in accordance with claim 1, wherein at least one of said columns lies outside the plane defined by two other of said columns.

3. A multi-phase high voltage transformer comprising a rounded high voltage terminal, a plurality of magnetic columns having electrically insulating properties along the lines of magnetic flux extending radially outward from said high voltage terminal, grounded magnetic circuit elements connecting the peripheral extremities of said insulating cores, a plurality of primary coils linking said grounded magnetic circuit elements, a plurality of secondary coils linking said columns and electrically connected between said high voltage terminal and said grounded magnetic elements and means for introducing multi-phase electric power into said primary coils, whereby multi-phase high voltage is produced at said highvoltage terminal.

4. A multi-phase high voltage transformer. comprising a rounded high voltage terminal, a plurality of magnetic columns having electrically insulating properties along the lines of magnetic flux extending radially, outward from References Cited in the fil'eof'this patent UNITED STATES PATENTS 422,746v Dolivo-Dobrowolsky Mar. 4, 1890 526,063 Wagemanm- Sept. 18, 1894 1,234,099 Lendi July 17, 1917 1,357,223 Chubb Nov. 2, 1920 1,874,109 Marbury Aug. 30, 1932 2,406,704 Mossayet al Aug. 27, 1946 OTHER REFERENCES Abstract, Electric and Magnetic Circuit Coupling Methods and Apparatus, Alexander S. Langsdorf, Jr., Chicago, Ill., filed Feb. 23, 1951, published June 30, 1953.. 

